Zebra mussels are small molluses of the Dreissena genus native to European water bodies and have recently been detected in large numbers in North America.
The spread of Dreissena species is of great concern to municipal, utility, and environmental interests because of the propensity of these species to form thick colonies. The formation of these colonies can have many effects, such as, for example, occluding structures such as water intake pipes, thus reducing the volume of water delivered, and degrading water quality and purity. Widespread unchecked colonization of Dreissena therefore threatens the operation of such industries as power plants, which rely on raw water for operation. In addition, Dreissena species kill many native bivalves such as unionid mussels, and the like, as well as consume ecologically important microscopic plankton.
Mechanical removal of the colonies is difficult and costly. Filtration of large volumes of intake water is impractical considering the small size (40 to 290 microns) of the colonizing larvae. Thermal or chemical treatment (e.g. hot water or chlorine) of intake water can be effective, but may have undesirable environmental consequences in some large-scale operations. Regulatory agencies continue to warn industries that continued long-term use of chemical and thermal control methods will be limited. A practical and economical method that reduces Dreissena colonization without adverse environmental impacts is therefore highly desirable.
The use of microorganisms such as bacteria or their chemical products to control pest populations is well known in the art. Bacillus thuringiensis varieties, for example, have been used for many years as a commercial insecticide for lepidopteran pests. More recently, additional strains of B. thuringiensis have been discovered which have specificity for an expanded range of pest populations, including, for example, mosquitoes, black flies, beetles, and the like.
Another bacterium, Serratia liquefaciens, has been shown to be lethal to zebra mussels (Toews et al., Can J Zool., Vol. 71, 1763 (1993)). To date, however, there has been no recognition of a strain of Pseudomonas that has a demonstrated ability to specifically control Dreissena species.